Re: Want to build a precision rifle need help.
SDHog,
If you are building an M-40A3/5 type rifle for sentimental or other training reasons, I'd recommend staying with the .308 Winchester for your first build. Good ammo is everywhere, you are familiar with the trajectory of the cartridge, it fits in your gear, its good enough for the military,etc.
Everyone needs, or should have, a good solid, accurate .308 Winchester in this day and age. Perhaps everyone who has built their first custom rifle thinks it will be their last (the perfect rifle). Most of us who did that have already built our second or third, or... tenth custom rifle since. Those that have not are planning one, I'd bet.
Once you get back to the States and get off base and away from ammo and arms issued by the governement, you will find the need/want to have something more efficient and capable of distance than the .308 (.260, .243, 6.5...) There is nothing wrong with that. You will never want to part with the .308 if your builder has done it right. You will just want a second or third rifle. Nothing wrong with that, either.
I've been in a similar situation to you right now. I managed without the help of the internet and still own all of the rifles I have ever owned with no regrets. Build a .308 M-40 clone (because you know what you like and dislike about it, it is known to you) and fully expect to keep it until you have figured out what number two will look like (will become known through additional exposure and experience off base around civilians).
Thanks for your service and stay safe, Jarhead. If you don't like my comments, you can call me an a-hole. I don't care. You can't hurt me with a word, typed or spoken.
Semper fi,